The present invention relates generally to heat exchange apparatus for use in combination with flue means conducting heated gases from a combustion zone, and more specifically to such a heat exchange means which is provided with internal baffling so as to control the amount of energy extracted from the heated gases.
In the past, heat exchange systems have been proposed for use in combination with flue means conducting heated gases from combustion zones. The fundamental purpose of the devices or systems is to extract thermal energy from stack gases, normally stack gases which carry products of combustion from a heating furnace or the like. Furnaces for residential dwellings are normally designed for use with conventional fuels, such as natural gas, fuel oil, or the like. The stacks or flues for these furnaces are designed to operate at a certain temperature level which is sufficiently high so as to prevent any unusual build-up or accumulation of condensate from the products of combustion.
In the conventional fuels, water is one of the primary products of combustion, and in order to prevent condensation build-up or freezing of the water, the stack temperature must be maintained at a sufficiently high level. Furthermore, elevated stack temperatures are required for controlling the movement of products of combustion through the system.
It is recognized that a substantial quantity of thermal energy is lost from residential furnaces through failure to recover energy otherwise dissipated through the flue or chimney. The amount of such excess losses will, of course, be variable and substantially unique for each individual installation. Therefore, in order to design a system for extracting thermal energy from the flues conducting heated gases from combustion zones, a number of variables must be taken into consideration, including particularly the amount of energy which may be extracted from the flue in order to continue to maintain appropriate stack temperatures, and preventing build-up of condensation and possible freezing thereof. The apparatus of the present invention provides a means for controllably adjusting the amount of heat to be extracted from the flue gases consistent with the requirements of the furnace flue, stack or chimney, thereby permitting the extraction of that amount of thermal energy which is in excess of that which is required for maintaining the appropriate stack temperature.